Unanticipated frequency and consequences of regimen-related diarrhea in patients being treated with radiation or chemoradiation regimens for cancers of the head and neck or lung.

Purpose: To better understand the indirect effects of standard courses of radiation therapy (RT) on distant tissue toxicity, we evaluated the frequency, course, and health and economic burden of regimen-related diarrhea in a large, multinational group of patients who were being treated for cancers of the head and neck (HNC) or lung (NSCLC).

Methods: In this exploratory, prospective study, 284 patients being treated for HNC and 60 being treated for NSCLC were stratified into four cohorts to evaluate the effect of radiation alone and radiation plus concomitant chemotherapy (CRT) on radiation-induced diarrhea (RID). RID was assessed daily throughout RT using a patient-reported five-point categorical scale. Health and resource use outcomes were evaluated at least weekly during radiation.

Results: Moderate to severe RID was reported in all groups and was worse among patient being treated with concomitant chemoradiation (CRT). Whereas 29 % of patients treated with radiation only developed RID, the incidence was 42 % among CRT-treated patients. Tumor site did not impact the rate of RID, but did impact the rate of development and was more acute in patients being treated for NSCLC than for HNC. Patients with significant RID had worse health and resource use outcomes than did patients without RID regardless of the form of treatment. G-tube placement, weight loss, unplanned office visits, and in-patient days were adversely affected by RID. Not surprisingly, patients treated with CRT had poorer health and resource outcomes than RT only patients, even in the absence of RID.

Conclusion: In addition to local tissue toxicities, our results suggest that focal radiation may also be associated with significant distant tissue-centric injury here represented by RID. While these changes were seen with radiation alone, the addition of chemotherapy increased the incidence and burden of illness. RID adversely impacted resource use. This unanticipated finding supports the hypothesis that focal radiation therapy results in pathobiological changes that extend beyond the radiation field and which can produce distant changes.